Atmospheric chemistry is a branch of
atmospheric science
Atmospheric science is the study of the Earth's atmosphere and its various inner-working physical processes. Meteorology includes atmospheric chemistry and atmospheric physics with a major focus on weather forecasting. Climatology is the study ...
in which the
chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, proper ...
of the
Earth's atmosphere
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing fo ...
and that of other planets is studied. It is a
multidisciplinary approach
Interdisciplinarity or interdisciplinary studies involves the combination of multiple academic disciplines into one activity (e.g., a research project). It draws knowledge from several other fields like sociology, anthropology, psychology, ec ...
of research and draws on
environmental chemistry
Environmental chemistry is the scientific study of the chemical and biochemical phenomena that occur in natural places. It should not be confused with green chemistry, which seeks to reduce potential pollution at its source. It can be defined as ...
,
physics
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which ...
,
meteorology
Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did no ...
,
computer modeling
Computer simulation is the process of mathematical modelling, performed on a computer, which is designed to predict the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be dete ...
,
oceanography
Oceanography (), also known as oceanology and ocean science, is the scientific study of the oceans. It is an Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dynami ...
,
geology
Geology () is a branch of natural science concerned with Earth and other Astronomical object, astronomical objects, the features or rock (geology), rocks of which it is composed, and the processes by which they change over time. Modern geology ...
and
volcanology
Volcanology (also spelled vulcanology) is the study of volcanoes, lava, magma and related geological, geophysical and geochemical phenomena (volcanism). The term ''volcanology'' is derived from the Latin word '' vulcan''. Vulcan was the an ...
and other disciplines. Research is increasingly connected with other areas of study such as
climatology
Climatology (from Greek , ''klima'', "place, zone"; and , '' -logia'') or climate science is the scientific study of Earth's climate, typically defined as weather conditions averaged over a period of at least 30 years. This modern field of stu ...
.
The composition and chemistry of the Earth's atmosphere is of importance for several reasons, but primarily because of the interactions between the atmosphere and
living organisms
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fun ...
. The composition of the Earth's atmosphere changes as result of natural processes such as
volcano
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most often found where tectonic plates ...
emissions,
lightning
Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions, both in the atmosphere or with one on the ground, temporarily neutralize themselves, causing the instantaneous release of an average ...
and bombardment by solar particles from
corona
Corona (from the Latin for 'crown') most commonly refers to:
* Stellar corona, the outer atmosphere of the Sun or another star
* Corona (beer), a Mexican beer
* Corona, informal term for the coronavirus SARS-CoV-2, which causes the COVID-19 di ...
. It has also been changed by human activity and some of these changes are harmful to human health, crops and ecosystems. Examples of problems which have been addressed by atmospheric chemistry include
acid rain
Acid rain is rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but ac ...
,
ozone depletion
Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozone lay ...
,
photochemical smog
Smog, or smoke fog, is a type of intense air pollution. The word "smog" was coined in the early 20th century, and is a portmanteau of the words ''smoke'' and ''fog'' to refer to smoky fog due to its opacity, and odor. The word was then inten ...
,
greenhouse gas
A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse ...
es and
global warming
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
. Atmospheric chemists seek to understand the causes of these problems, and by obtaining a theoretical understanding of them, allow possible solutions to be tested and the effects of changes in government policy evaluated.
Atmospheric composition
Trace gas composition
Besides the more major components listed above, Earth's atmosphere also has many trace gas species that vary significantly depending on nearby sources and sinks. These trace gases can include compounds such as
CFCs/HCFCs which are particularly damaging to the ozone layer, and
which has a characteristic foul odor of rotten eggs and can be smelt in concentrations as low as 0.47 ppb. Some ''approximate'' amounts near the surface of some additional gases are listed below. In addition to gases, the atmosphere contains particulates as
aerosol
An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...
, which includes for example droplets, ice crystals, bacteria, and dust.
History
The ancient
Greeks
The Greeks or Hellenes (; el, Έλληνες, ''Éllines'' ) are an ethnic group and nation indigenous to the Eastern Mediterranean and the Black Sea regions, namely Greece, Cyprus, Albania, Italy, Turkey, Egypt, and, to a lesser extent, oth ...
regarded air as one of the
four elements
Classical elements typically refer to earth, water, air, fire, and (later) aether which were proposed to explain the nature and complexity of all matter in terms of simpler substances. Ancient cultures in Greece, Tibet, and India had simi ...
. The first scientific studies of atmospheric composition began in the 18th century, as chemists such as
Joseph Priestley
Joseph Priestley (; 24 March 1733 – 6 February 1804) was an English chemist, natural philosopher, separatist theologian, grammarian, multi-subject educator, and liberal political theorist. He published over 150 works, and conducted exp ...
,
Antoine Lavoisier
Antoine-Laurent de Lavoisier ( , ; ; 26 August 17438 May 1794), When reduced without charcoal, it gave off an air which supported respiration and combustion in an enhanced way. He concluded that this was just a pure form of common air and th ...
and
Henry Cavendish
Henry Cavendish ( ; 10 October 1731 – 24 February 1810) was an English natural philosopher and scientist who was an important experimental and theoretical chemist and physicist. He is noted for his discovery of hydrogen, which he termed "infl ...
made the first measurements of the composition of the atmosphere.
In the late 19th and early 20th centuries interest shifted towards trace constituents with very small concentrations. One particularly important discovery for atmospheric chemistry was the discovery of
ozone
Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
by
Christian Friedrich Schönbein
Christian Friedrich Schönbein H FRSE(18 October 1799 – 29 August 1868) was a German-Swiss chemist who is best known for inventing the fuel cell (1838) at the same time as William Robert Grove and his discoveries of guncotton and ozone.
Lif ...
in 1840.
In the 20th century atmospheric science moved on from studying the composition of air to a consideration of how the concentrations of trace gases in the atmosphere have changed over time and the chemical processes which create and destroy compounds in the air. Two particularly important examples of this were the explanation by
Sydney Chapman and
Gordon Dobson of how the
ozone layer
The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the atmosphere, although still small in rela ...
is created and maintained, and the explanation of
photochemical smog
Smog, or smoke fog, is a type of intense air pollution. The word "smog" was coined in the early 20th century, and is a portmanteau of the words ''smoke'' and ''fog'' to refer to smoky fog due to its opacity, and odor. The word was then inten ...
by
Arie Jan Haagen-Smit. Further studies on ozone issues led to the 1995 Nobel Prize in Chemistry award shared between
Paul Crutzen
Paul Jozef Crutzen (; 3 December 1933 – 28 January 2021) was a Dutch meteorologist and atmospheric chemist. He was awarded the Nobel Prize in Chemistry in 1995 for his work on atmospheric chemistry and specifically for his efforts in studying ...
,
Mario Molina
Mario José Molina-Pasquel Henríquez (19 March 19437 October 2020), known as Mario Molina, was a Mexican chemist. He played a pivotal role in the discovery of the Antarctic ozone hole, and was a co-recipient of the 1995 Nobel Prize in Chemis ...
and
Frank Sherwood Rowland
Frank Sherwood "Sherry" Rowland (June 28, 1927 – March 10, 2012) was an American Nobel laureate and a professor of chemistry at the University of California, Irvine. His research was on atmospheric chemistry and chemical kinetics. His be ...
.
In the 21st century the focus is now shifting again. Atmospheric chemistry is increasingly studied as one part of the
Earth system
Earth system science (ESS) is the application of systems science to the Earth. In particular, it considers interactions and 'feedbacks', through material and energy fluxes, between the Earth's sub-systems' cycles, processes and "spheres"— atmo ...
. Instead of concentrating on atmospheric chemistry in isolation the focus is now on seeing it as one part of a single system with the rest of the
atmosphere
An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...
,
biosphere
The biosphere (from Greek βίος ''bíos'' "life" and σφαῖρα ''sphaira'' "sphere"), also known as the ecosphere (from Greek οἶκος ''oîkos'' "environment" and σφαῖρα), is the worldwide sum of all ecosystems. It can also be ...
and
geosphere
There are several conflicting usages of geosphere, variously defined. It may be taken as the collective name for the lithosphere, the hydrosphere, the cryosphere, and the atmosphere. The different collectives of the geosphere are able to exchange ...
. An especially important driver for this is the links between chemistry and
climate
Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologic ...
such as the effects of changing climate on the recovery of the ozone hole and vice versa but also interaction of the composition of the atmosphere with the oceans and terrestrial
ecosystems
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
.
Methodology
Observations, lab measurements, and modeling are the three central elements in atmospheric chemistry. Progress in atmospheric chemistry is often driven by the interactions between these components and they form an integrated whole. For example, observations may tell us that more of a chemical compound exists than previously thought possible. This will stimulate new modelling and laboratory studies which will increase our scientific understanding to a point where the observations can be explained.
Observation
Observations of atmospheric chemistry are essential to our understanding. Routine observations of chemical composition tell us about changes in atmospheric composition over time. One important example of this is the
Keeling Curve - a series of measurements from 1958 to today which show a steady rise in of the concentration of
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
(see also
ongoing measurements of atmospheric CO2). Observations of atmospheric chemistry are made in observatories such as that on
Mauna Loa
Mauna Loa ( or ; Hawaiian: ; en, Long Mountain) is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaii in the Pacific Ocean. The largest subaerial volcano (as opposed to subaqueous volcanoes) in both mass and ...
and on mobile platforms such as aircraft (e.g. the UK's
Facility for Airborne Atmospheric Measurements), ships and balloons. Observations of atmospheric composition are increasingly made by
satellites with important instruments such as
GOME and
MOPITT
MOPITT (Measurements of Pollution in the Troposphere) is a payload scientific instrument launched into Earth orbit by NASA on board the Terra satellite in 1999. It is designed to monitor changes in pollution patterns and its effect in the lower ...
giving a global picture of air pollution and chemistry. Surface observations have the advantage that they provide long term records at high time resolution but are limited in the vertical and horizontal space they provide observations from. Some surface based instruments e.g.
LIDAR
Lidar (, also LIDAR, or LiDAR; sometimes LADAR) is a method for determining ranges (variable distance) by targeting an object or a surface with a laser and measuring the time for the reflected light to return to the receiver. It can also be ...
can provide concentration profiles of chemical compounds and aerosol but are still restricted in the horizontal region they can cover. Many observations are available on line in
Atmospheric Chemistry Observational Databases.
Laboratory studies
Measurements made in the laboratory are essential to our understanding of the sources and sinks of pollutants and naturally occurring compounds. These experiments are performed in controlled environments that allow for the individual evaluation of specific chemical reactions or the assessment of properties of a particular atmospheric constituent.
Types of analysis that are of interest includes both those on gas-phase reactions, as well as
heterogeneous
Homogeneity and heterogeneity are concepts often used in the sciences and statistics relating to the uniformity of a substance or organism. A material or image that is homogeneous is uniform in composition or character (i.e. color, shape, siz ...
reactions that are relevant to the formation and growth of
aerosol
An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...
s. Also of high importance is the study of atmospheric
photochemistry
Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 nm), visible light (400–7 ...
which quantifies how the rate in which molecules are split apart by sunlight and what resulting products are. In addition,
thermodynamic
Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of ther ...
data such as
Henry's law
In physical chemistry, Henry's law is a gas law that states that the amount of dissolved gas in a liquid is directly proportional to its partial pressure above the liquid. The proportionality factor is called Henry's law constant. It was formulat ...
coefficients can also be obtained.
Modeling
In order to synthesize and test theoretical understanding of atmospheric chemistry, computer models (such as
chemical transport model A chemical transport model (CTM) is a type of computer numerical model which typically simulates atmospheric chemistry and may give air pollution forecasting
Air pollution forecasting is the application of science and technology to predict the co ...
s) are used. Numerical models solve the differential equations governing the concentrations of chemicals in the atmosphere. They can be very simple or very complicated. One common trade off in numerical models is between the number of chemical compounds and chemical reactions modeled versus the representation of transport and mixing in the atmosphere. For example, a box model might include hundreds or even thousands of chemical reactions but will only have a very crude representation of mixing in the atmosphere. In contrast, 3D models represent many of the physical processes of the atmosphere but due to constraints on computer resources will have far fewer chemical reactions and compounds. Models can be used to interpret observations, test understanding of chemical reactions and predict future concentrations of chemical compounds in the atmosphere. these models can be global (simulating the entire earth) or they can be regional (focused on only a specific region). The trade-off between the two approaches is their resolution as well as the amount of detail they can provide; global models usually have lower horizontal resolution and represent less complex chemical mechanisms but they simulate a larger area, while regional models do not simulate the entire globe but focus on one area with higher resolution and more detail. One important current trend is for atmospheric chemistry modules to become one part of earth system models in which the links between climate, atmospheric composition and the biosphere can be studied. These types of models allow the coupling of different compartments of the earth, such as the atmosphere, the biosphere and the hydrosphere; allowing the users to analyze the complicated interactions between them.
Some models are constructed by automatic code generators (e.g.
Autochem
AutoChem is NASA release software that constitutes an automatic computer code generator and documenter for chemically reactive systems written by David Lary between 1993 and the present. It was designed primarily for modeling atmospheric chemis ...
or
Kinetic PreProcessor
The Kinetic PreProcessor (KPP) is an open-source software tool used in atmospheric chemistry. Taking a set of chemical reactions and their rate coefficients as input, KPP generates Fortran 90, FORTRAN 77, C, or Matlab code
of the resulting or ...
). In this approach a set of constituents are chosen and the automatic code generator will then select the reactions involving those constituents from a set of reaction databases. Once the reactions have been chosen the
ordinary differential equations
In mathematics, an ordinary differential equation (ODE) is a differential equation whose unknown(s) consists of one (or more) function(s) of one variable and involves the derivatives of those functions. The term ''ordinary'' is used in contrast w ...
that describe their time evolution can be automatically constructed.
See also
*
Oxygen cycle
Oxygen cycle refers to the movement of oxygen through the atmosphere (air), biosphere (plants and animals) and the lithosphere (the Earth’s crust). The oxygen cycle demonstrates how free oxygen is made available in each of these regions, as wel ...
*
Ozone-oxygen cycle
*
Paleoclimatology
Paleoclimatology (British spelling, palaeoclimatology) is the study of climates for which direct measurements were not taken. As instrumental records only span a tiny part of Earth's history, the reconstruction of ancient climate is important to ...
*
Scientific Assessment of Ozone Depletion
The Scientific Assessment of Ozone Depletion is a sequence of reports sponsored by WMO/UNEP. The most recent report is from 2018. The reports were set up to inform the Montreal Protocol and amendments about ozone depletion.
Background
The Mont ...
*
Tropospheric ozone depletion events
References
Further reading
* Brasseur, Guy P.; Orlando, John J.; Tyndall, Geoffrey S. (1999). ''Atmospheric Chemistry and Global Change''. Oxford University Press. .
* Finlayson-Pitts, Barbara J.; Pitts, James N., Jr. (2000). ''Chemistry of the Upper and Lower Atmosphere''. Academic Press. .
* Seinfeld, John H.; Pandis, Spyros N. (2006). ''Atmospheric Chemistry and Physics: From Air Pollution to Climate Change'' (2nd Ed.). John Wiley and Sons, Inc. .
* Warneck, Peter (2000). ''Chemistry of the Natural Atmosphere'' (2nd Ed.). Academic Press. .
* Wayne, Richard P. (2000). ''Chemistry of Atmospheres'' (3rd Ed.). Oxford University Press. .
*J. V. Iribarne, H. R. Cho, ''Atmospheric Physics'', D. Reidel Publishing Company, 1980
External links
WMO Scientific Assessment of Ozone Depletion: 2006IGAC The International Global Atmospheric Chemistry ProjectPaul Crutzen Interview- freeview video of
Paul Crutzen
Paul Jozef Crutzen (; 3 December 1933 – 28 January 2021) was a Dutch meteorologist and atmospheric chemist. He was awarded the Nobel Prize in Chemistry in 1995 for his work on atmospheric chemistry and specifically for his efforts in studying ...
Nobel Laureate for his work on decomposition of ozone, talking to Nobel Laureate
Harry Kroto
Sir Harold Walter Kroto (born Harold Walter Krotoschiner; 7 October 1939 – 30 April 2016), known as Harry Kroto, was an English chemist. He shared the 1996 Nobel Prize in Chemistry with Robert Curl and Richard Smalley for their discovery of ...
, the
Vega Science Trust
The Vega Science Trust was a not-for-profit organisation which provided a platform from which scientists can communicate directly with the public on science by using moving image, sound and other related means. The Trust closed in 2012 but the web ...
The Cambridge Atmospheric Chemistry Databaseis a large constituent observational database in a common format.
*
ttp://jpldataeval.jpl.nasa.gov/index.html NASA-JPL Chemical Kinetics and Photochemical Data for Use in Atmospheric Studiesbr>
Kinetic and photochemical data evaluated by the IUPAC Subcommittee for Gas Kinetic Data Evaluationat
Sam Houston State University
Sam Houston State University (SHSU or Sam) is a public university in Huntsville, Texas. It was founded in 1879 and is the third-oldest public college or university in Texas. It is one of the first normal schools west of the Mississippi River and ...
Tropospheric chemistry
{{Branches of chemistry
Atmospheric Chemistry
Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earth's atmosphere and that of other planets is studied. It is a multidisciplinary approach of research and draws on environmental chemistry, physics, meteoro ...
Environmental chemistry
Chemistry